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Description
Dr. Manton is a cat breeder and she explains the process of artificial selection starting with a Siamese cat crossed with a Persian and ending with several exotic variations after years of careful
...breeding and crossing.
In natural selection a mutation will only make itself felt in the population if it confers on the individual some selective advantage.
The points to be made are that selection is a very real thing and
can be very exactly controlled. That a knowledge of genetics is of
tremendous importance to anyone who breeds animals or plants and that the nature of a species, even humans, could be changed by selection.
| 23 | 00:02:02,000 | 00:02:08,000 | Some of these will be pure for black, some of them will be carrying the pattern. |
| 28 | 00:02:06,000 | 00:02:12,000 | Now if I take away the top of the trap you can see that the moths… |
| 24 | 00:02:09,000 | 00:02:13,000 | Some of these will be pure for black, others will carry the pattern and the same there. |
| 29 | 00:02:13,000 | 00:02:18,000 | ..come to rest under these egg cartons and when they’re disturbed, |
| 25 | 00:02:14,000 | 00:02:18,000 | But the only cat in the whole lot, of one in sixteen of the offspring… |
| 26 | 00:02:19,000 | 00:02:23,000 | ..which carries the two recessive characters, the long hair… |
| 30 | 00:02:19,000 | 00:02:22,000 | many of them fly away, as they’re doing now. |
| 27 | 00:02:24,000 | 00:02:28,000 | ..and the Siamese colour pattern is this and it breeds true. |
| 31 | 00:02:24,000 | 00:02:28,000 | In May to July, some of the moths we catch are… |
| 28 | 00:02:29,000 | 00:02:30,000 | (Michael Pentz) So that’s your true breed. That’s in fact your target. |
| 32 | 00:02:29,000 | 00:02:33,000 | ..specimens of the Peppered Moth and I have two here. |
| 29 | 00:02:30,000 | 00:02:31,000 | (Sidnie Manton) Yes. |
| 30 | 00:02:32,000 | 00:02:34,000 | Michael Pentz: Now, having got that far, what’s the next move? |
| 31 | 00:02:34,000 | 00:02:36,000 | Do you just breed out from this particular cat? |
| 33 | 00:02:35,000 | 00:02:39,000 | Although they look very different, these two are in fact varieties of… |
| 32 | 00:02:37,000 | 00:02:40,000 | (Michael Pentz) Is that the best way to proceed or what did you do in fact? |
| 34 | 00:02:40,000 | 00:02:43,000 | ..the same species - the Peppered Moth - differing from just one gene. |
| 33 | 00:02:41,000 | 00:02:45,000 | Sidnie Manton: Well we do two things, partly, mating that to that and proceeding… |
| 35 | 00:02:44,000 | 00:02:48,000 | If the black is crossed with the pale then the black is dominant. |
| 34 | 00:02:46,000 | 00:02:50,000 | ..by selection as was largely done in America too, but a much more… |
| 36 | 00:02:49,000 | 00:02:53,000 | 100 years ago the black form was very rare which is why we call… |
| 35 | 00:02:51,000 | 00:02:55,000 | ..profitable way is to pay great attention to the genetics of your animals and… |
| 37 | 00:02:54,000 | 00:02:59,000 | ..the pale form variety Typica, and we recognise the black as being a mutant. |
| 36 | 00:02:56,000 | 00:03:01,000 | ..plan your breeding and back cross to Persians carrying this colour point pattern. |
| 38 | 00:03:01,000 | 00:03:05,000 | About 20 years ago, Doctor Kettlewell of Oxford University carried out… |
| 37 | 00:03:02,000 | 00:03:08,000 | And if you cross those two you will step up the Persian characteristics that… |
| 39 | 00:03:06,000 | 00:03:11,000 | ..a survey of the Peppered Moth populations. This map shows his results. |
| 38 | 00:03:09,000 | 00:03:17,000 | ..you see up there and in about four, five, six, I suppose eight generations altogether, |
| 40 | 00:03:13,000 | 00:03:17,000 | The circles represent his sampling sites, the area represents the total number… |
| 39 | 00:03:18,000 | 00:03:23,000 | we have achieved cats which look like this, you see, very different from that. |
| 41 | 00:03:18,000 | 00:03:21,000 | ..of moths he caught, and the black and white segments show… |
| 42 | 00:03:22,000 | 00:03:25,000 | ..the relative proportions of the black, of the pale and dark mutants. |
| 40 | 00:03:24,000 | 00:03:28,000 | With the short nose, the wide head, approximating much more… |
| 43 | 00:03:26,000 | 00:03:28,000 | Now let’s look at the distribution. |
| 41 | 00:03:29,000 | 00:03:31,000 | ..to the Persian ancestor up there. |
| 44 | 00:03:29,000 | 00:03:35,000 | Here in the industrial Midlands and the North and the South and South East, |
| 42 | 00:03:32,000 | 00:03:34,000 | Michael Pentz: I see that Peggy Varley has got one of them right here… |
| 43 | 00:03:34,000 | 00:03:35,000 | ..which perhaps we could show it. |
| 44 | 00:03:37,000 | 00:03:39,000 | Sidnie Manton: Well this is a primitive colour point. She’s about 15. |
| 45 | 00:03:40,000 | 00:03:43,000 | Much too dark in the body, a good top to her head, |
| 46 | 00:03:41,000 | 00:03:44,000 | also true downwind of these industrial areas. |
| 46 | 00:03:44,000 | 00:03:49,000 | ears a bit too big, nose ever so much too long but she at least was a beginning. |
| 47 | 00:03:45,000 | 00:03:51,000 | But in the west of Britain the pale form is the common one. |
| 47 | 00:03:50,000 | 00:03:55,000 | Now contrast that with a blue point, now, the last was a seal point… |
| 48 | 00:03:53,000 | 00:03:58,000 | Now how can we explain this? We must think about how the moths live. |
| 48 | 00:03:56,000 | 00:03:59,000 | ..this is a blue point and you get this grey colour to the ears with… |
| 49 | 00:03:59,000 | 00:04:03,000 | They fly by night but in the day they rest on tree trunks. |
| 49 | 00:04:00,000 | 00:04:05,000 | ..a blue dilution factor added and you see a much more Persian face. |
| 50 | 00:04:04,000 | 00:04:09,000 | This trunk has grey bark and it has lichen growing over it… |
| 50 | 00:04:06,000 | 00:04:11,000 | The fur will get much longer; this is an eight month old, purr purr. |
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